CMUT devices are becoming increasingly popular in medical applications. For example, CMUT devices have been used to improve medical ultrasound imaging probes. CMUT devices have also been used to provide high-intensity focused ultrasound for use in medical therapy. Additionally, CMUT devices can be used to generate airborne ultrasound for multiple applications including gesture sensing and gas flow monitoring. Conventional CMUT devices are typically produced directly on a silicon substrate (i.e. on a silicon wafer). For instance, conventional CMUT devices are often fabricated using a micro-electro-mechanical system (MEMS) manufacturing technique in which a release layer is etched out, leaving a free-standing (flexible) membrane. The top of the membrane is typically metalized to reduce the resistance of the top (electrode) plate, and the membrane is then used as a transducer to transmit and receive ultrasonic signals.
CMUT devices (a CMUT die or array) are comprised of one or more CMUT elements, and each CMUT element can contain one of more CMUT cells. Conventional CMUT devices utilize bond pads to provide electrical contact to the top plate for each of the CMUT elements in the array, such as a plurality of bond pads for a CMUT device including a plurality of CMUT elements arranged in a CMUT array. Since the bond wire is elevated above the bond pad, the bond pad is placed remote from the CMUT elements in the CMUT array to facilitate packaging. This constraint not only increases the CMUT array die size due to the need for interconnect routing lines, but also reduces performance and complicates the packaging process. Both the increased die size and the complicated packaging process increase the cost of packaged CMUT die.